Comparison of hydrostatic head of polyester and silnylon

[telemarktim]

It is quite understandable that some would think that it is quite inappropriate to make a DIY backpacking tent out of polyester umbrella fabric that has no waterproofing or DWR treatment. Consequently, silnylon is commonly used as an alternative.
I experimented with making tents with this breathing polyester and unlike silnylon the fabric has the advantage of staying taught when wet and cold, forming minimal condensation inside and it dries much more quickly at pack-up time on cold mornings. Both fabrics shed heavy rain quite well as shown in this video tour of my silnylon and polyester pyramid tents during heavy rain.


Given the good performance of of the polyester fabric, I was curious to see how it compared with silnylon with regard to withstanding a hydrostatic head test using a 500mm column of water.
For this testing, I made a sealed tube of the silnylon using RTV silicone rubber as glue. The polyester does not bond so strongly with the silicone rubber, so I first glued the the tube (with silver coating on the outside) with the rubber and then folded the seam back on itself and sewed through it while the rubber was still in a liquid state. I also sealed the stitches from both sides with my DIY seam sealer made from silicone rubber diluted with mineral turpentine. I view the rubber as acting as a sealing gasket rather than as a glue in this situation and the seam did not appear to leak.

I marked a series of line on the tubes at 100mm intervals from the bottom. When ‘filled’ to 500mm level, both fabrics immediately leaked a lot as shown in the video below:


To quantify the leakage rate, I placed a bowl under each tube and collected the drips over 35 minutes and they leaked 24g (polyester) and 32g (silnylon). I think that this shows that polyester is no leakier than silnylon and probably less so. I hasten to add that both make excellent tents for protection from rain or snow, but polyester appears to have many advantages over silnylon.
For more details of my investigation of these issues please see:
https://timtinker.com/polyester-silnylon-hydrostatic-head/

Tim

[Lamont]

Nice work again Tim.

Last edited by Lamont on Fri 17 Feb, 2023 4:42 pm, edited 1 time in total.

[Franco]

Same comment as for tear strength.
You can get silnylon with 800mm HH as you can get the 5000mm type.
For one , Tarptent started with the then available in the USA 1200/1500mm type, then went with a 2000mm version and, for the last few years, a South Korean made 3000mm type.

[telemarktim]

Same comment as for tear strength.
You can get silnylon with 800mm HH as you can get the 5000mm type.
For one , Tarptent started with the then available in the USA 1200/1500mm type, then went with a 2000mm version and, for the last few years, a South Korean made 3000mm type.

Hi Franko, I have just reported my HH testing of two different fabrics. I think the tests are simple and valid and transparent. From practical experience, both fabrics shed rainwater well when used for making pyramid tents, but they both leak with this mild HH test. The point of doing the test was to point out that the silnylon was no better than the unproofed polyester which does not wet/stretch or collect condensation as silnylon does. Just putting some objective measurements in to help to understand the good performance of the polyester tent fabric. Likewise, regarding your comment about my comparative load-bearing tests. Tim

[Franco]

"The point of doing the test was to point out that the silnylon was no better than the unproofed polyester which does not wet/stretch or collect condensation as silnylon does"
yes but it is misleading to call it a test of silnylon vs polyester when in fact it is a test of that silnylon versus that polyester.

[telemarktim]

"The point of doing the test was to point out that the silnylon was no better than the unproofed polyester which does not wet/stretch or collect condensation as silnylon does"
yes but it is misleading to call it a test of silnylon vs polyester when in fact it is a test of that silnylon versus that polyester.

Hi Franko, I just did a comparison and reported the results. You introduced the terms 'VS' and 'versus' so there is nothing misleading in my report. If you wanted to say that was a test of silnylon vs polyester or polyester vs silnylon, I would be happy, but it makes no difference which comes first. Tim

[Warin]

If you wanted to say that was a test of silnylon vs polyester or polyester vs silnylon, I would be happy, but it makes no difference which comes first. Tim

What he is trying to say is not all silnylon are the same. nor all silpolys...

What you tested was one silnylon against one silpoly. And that was informative to me, does it hold true for all, no ... but it is a one sample.

[Franco]

If you wanted to say that was a test of silnylon vs polyester or polyester vs silnylon, I would be happy, but it makes no difference which comes first. Tim[/quote]
I am just reading the title
"comparison of hydrostatic head of polyester and silnylon" so I am not sure why you are pretending that I introduced one vs the other when it is right there in your title.
Reading that some could get the impression that it is a valid test of those two types of fabric when (again_) I am pointing out that it is only relevant for the two you tested.
BTW, I post similar comments when folk talk about DCF and Tyvek (in particular) as if there was just one type for each .
I do that because at times it ends up with people debating the pros and cons not realising that they are talking about two or three very different materials.

[andrewa]

Franco, whilst you make a valid point that there are obviously various types of silinylon and polyester, you were the one that introduced the term “vs”….Tim did not…..he used the word “and”, which is not a comparison. It is 2 statements, non sequiteur. Readers may take it as “sequiteur”, but there was no implication that it was. I spent years doing medical exams where we were given 2 statements, had to decide whether each was true or false, and then work out whether they were sequiteur or not, pedantic as it may have seemed.

Andrew

[telemarktim]

If you wanted to say that was a test of silnylon vs polyester or polyester vs silnylon, I would be happy, but it makes no difference which comes first. Tim

What he is trying to say is not all silnylon are the same. nor all silpolys...

What you tested was one silnylon against one silpoly. And that was informative to me, does it hold true for all, no ... but it is a one sample.

Thanks Warin, The fabrics that were tested were the ones that I had on hand. I don't think either is particularly waterproof but my practical and subjective assessment of making and using tents made from them is, that they both make an effective rain-resistant shelter. Tim

[Franco]

"he used the word “and”, which is not a comparison"
Strange that because by the words "comparison of..." somehow I understand it is a comparison.
(it's in the title)

[andrewa]

Ok, I’ll cop that one. True.

A

[GPSGuided]

Indeed it’s a comparison that’s also misleading to those who did not know there can be spec differences within each fabric type. The OP should have stated the exact brand and spec of the fabrics used as one would expect in any technical paper or it’s pointless.

[Franco]

I'm honestly surprised that others did not bother to comment on that or it was not obvious to them.
But I see in the other thread that the point is still not understood.
I'm going to compare a Toyota Yaris with a made in China Skoda Octavia and call that thread Chinese and Japanese cars comparison or just conclude that Skoda is better than Toyota.
(yes ,I do see some like and apriciate the OP's efforts (I made many tests like that myself) but a casual read of them does lead to the wrong conclusion).

[telemarktim]

I'm honestly surprised that others did not bother to comment on that or it was not obvious to them.
But I see in the other thread that the point is still not understood.
I'm going to compare a Toyota Yaris with a made in China Skoda Octavia and call that thread Chinese and Japanese cars comparison or just conclude that Skoda is better than Toyota.
(yes ,I do see some like and apriciate the OP's efforts (I made many tests like that myself) but a casual read of them does lead to the wrong conclusion).

Hi Franko, What would make you happy?

I agree that the title may suggest to some people, like you, that it is a comparison of all silnylons and all polyesters that have ever been manufactured in the known universe and possibly other parallel ones. However, for most amateur MYOGer on this forum, I think they would expect less and my article clearly is not able to generalise to draw conclusions about all silnylons and all polyesters.

Perhaps you may be placated by changing the title to:
"Comparison of hydrostatic head of a polyester and a silnylon" and also the third last sentence to:
"I think that this shows that the polyester is no leakier than the silnylon and probably less so."
This would make sure that I was not trying to generalise for all fabrics.

However, I would need help, from forum management, to make such an edit at this late stage.
Tim

[Franco]

It isn't about me, just about getting the facts right.
I give yo another example of how things can be misintepreted.
Many years ago Ron Bell at Mountain Laurel Design used his own special name for the silnylon he was using (a bit like Hilleberg call theirs Kerlon).
Often when people were comparing MLD with Tarptent ,at the time, they were commenting that MLD used better silnylon. In fact it was the same stuff (not custom made) supplied by the same company. (the Westmark Corporation).
Because that "better silnylon" was then repeated, it became a fact (at least in the mind of some).
So what is different can be perceived to be the same and the same to be different.

[JohnnoMcJohnno]

Well done Tim.

And to other's here, I really don't get the criticism. It's a MYOG page. If you're making your own gear, you are going to buy your own materials. You can't always go off the spec, you don't always have the specs, you don't know how long its been hanging around in the warehouse, and none of us have the facilities that the tent manufacturer's have for testing stuff. And as Franco has pointed out, even the manufacturers can be guilty of stretching the truth. So as far as I am concerned, the OP has provided a simple but effective method that anyone can use to test the materials they have on hand. Which is a good thing!

[telemarktim]

Well done Tim.

And to other's here, I really don't get the criticism. It's a MYOG page. If you're making your own gear, you are going to buy your own materials. You can't always go off the spec, you don't always have the specs, you don't know how long its been hanging around in the warehouse, and none of us have the facilities that the tent manufacturer's have for testing stuff. And as Franco has pointed out, even the manufacturers can be guilty of stretching the truth. So as far as I am concerned, the OP has provided a simple but effective method that anyone can use to test the materials they have on hand. Which is a good thing!

Thanks Johnno, It is nice not to be treated a snake oil salesman. Although, I did see the similarity of my silnylon tube and a massive translucent shed skin from a tiger snake that I found in my citrus grove. It is hard to imagine how they get out and leave the skin with all the fine detail of eyes and lips. Maybe I can do a HH test on that. Maybe I just should have a video of the tube with the water pissing through it and let the reader guess what the unknown woven plastic polymer with silicone rubber coating was? Tim

[Lamont]

Well done Tim.

And to other's here, I really don't get the criticism. It's a MYOG page. .... So as far as I am concerned, the OP has provided a simple but effective method that anyone can use to test the materials they have on hand. Which is a good thing!

Nicely summed up Johnno.

Thanks Johnno, It is nice not to be treated a snake oil salesman. Although, I did see the similarity of my silnylon tube and a massive translucent shed skin from a tiger snake that I found in my citrus grove. It is hard to imagine how they get out and leave the skin with all the fine detail of eyes and lips. Maybe I can do a HH test on that. Maybe I just should have a video of the tube with the water pissing through it and let the reader guess what the unknown woven plastic polymer with silicone rubber coating was? Tim

Love your work Tim.